This document discusses herbal antimicrobials as an alternative to conventional antibiotics to address antimicrobial resistance (AMR). It provides information on the scope of AMR globally, including an estimated 1.27 million deaths directly attributable to resistance in 2019. The document then summarizes research on the antimicrobial properties of various herbs and oils, including carvacrol, ajowan oil, thyme oil, and cinnamaldehyde. It presents data on the susceptibility of different bacterial strains to these herbal antimicrobials. The document concludes by acknowledging limitations to the therapeutic use of herbal antimicrobials, such as a lack of quality control and defined therapeutic doses, but also their potential to be effective antimicrobial treatments.

1. Herbal Antimicrobials to Counter
AMR: An exploratory study
Bhoj R Singh
Principal Scientist and Head
Division of Epidemiology, ICAR-IVRI, Izatnagar-243122
Lecture on 21st February 2023. In: Antimicrobial Resistance (AMR) in Foodborne pathogens” sponsored
under the ICAR-NAHEP-CAAST project by the MAFSU, Mumbai Veterinary College, at the Division of
Veterinary Public Health, ICAR-IVRI from 20th February to 25th February, 2023.

2. Antimicrobial Drug-resistance (AMR)
As per the latest meta-analysis (https://doi.org/10.1016/S0140-6736) by Dr
Mohsen Naghavi, Institute for Health Metrics and Evaluation,
University of Washington, Seattle, WA 98195, USA nagham@uw.edu
• 1·27 million deaths were directly attributable to resistance in 2019.
• 4·95 million deaths were associated with bacteria
• Australasia had the lowest AMR burden in 2019, with 6·5 deaths per 100
000 attributable to AMR and 28·0 deaths per 100 000 associated with AMR
in 2019.
• Western sub-Saharan Africa had the highest burden, with 27·3 deaths per
100 000 attributable to AMR and 114·8 deaths per 100 000 associated with
AMR in 2019.
• Lower respiratory and thorax infections, bloodstream infections, and intra-
abdominal infections accounted for 78·8 of the deaths attributable to AMR
in 2019; lower respiratory infections alone accounted for more than 400
000 attributable deaths and 1·5 million associated deaths.

3. All-age rate of deaths attributable to and associated with bacterial antimicrobial
resistance by Global Burden of Disease (GBD) region, 2019
Estimates were aggregated across drugs, accounting for the co-occurrence of
resistance to multiple drugs. Error bars show 95% uncertainty intervals. GBD=Global
Burden of Diseases, Injuries, and Risk Factors Study.

4. Global deaths (counts) attributable to and associated with bacterial antimicrobial resistance by
infectious syndrome, 2019
Estimates were aggregated across drugs, accounting for the co-occurrence of resistance to multiple
drugs. Error bars show 95% uncertainty intervals. Does not include gonorrhoea and chlamydia
because we did not estimate the fatal burden of this infectious syndrome. Bone+=infections of
bones, joints, and related organs. BSI=bloodstream infections. Cardiac=endocarditis and other
cardiac infections. CNS=meningitis and other bacterial CNS infections. Intra-abdominal=peritoneal
and intra-abdominal infections. LRI+=lower respiratory infections and all related infections in the
thorax. Skin=bacterial infections of the skin and subcutaneous systems. TF–PF–iNTS= typhoid fever,
paratyphoid fever, and invasive non-typhoidal Salmonella spp. UTI=urinary tract infections and
pyelonephritis.

5. AMR Pathogens
The six leading pathogens for deaths associated with resistance included
Escherichia coli, followed by Staphylococcus aureus, Klebsiella
pneumoniae, Streptococcus pneumoniae, Acinetobacter baumannii, and
Pseudomonas aeruginosa.
The six pathogens were responsible for 929 000 (660 000–1 270 000) deaths
attributable to AMR and 3·57 million (2·62–4·78) deaths associated with
AMR in 2019.
Of the leading AMR pathogen-drug combinations, meticillin-resistant S.
aureus (MRSA), resistance was generally highest (60% to less than 80%) in
countries in north Africa and the Middle East (e.g., Iraq and Kuwait) and
lowest (less than 5%) in several countries in Europe and sub-Saharan
Africa. MRSA was responsible for more than 100,000 deaths and 3·5
million cases attributable to resistance
The isoniazid and rifampicin co-resistant (MDR excluding XDR) M.
tuberculosis, isolate resistance was highest (primarily 10% to less than
30%) in eastern Europe and under 5% in many countries around the world.
The other five groups are third-generation cephalosporin-resistant E. coli,
carbapenem-resistant A. baumannii, fluoroquinolone-resistant E. coli,
carbapenem-resistant K. pneumoniae, and third-generation
cephalosporin-resistant K. pneumoniae.

6. Global deaths (counts) attributable to and associated with bacterial antimicrobial
resistance by pathogen types, 2019
Estimates were aggregated across drugs, accounting for the co-occurrence of
resistance to multiple drugs. Error bars show 95% uncertainty intervals.

7. Therefore
• There is an urgent need to develop therapeutic interventions for the
treatment of AMR infections.
• Development of strong antimicrobial stewardship.
• Developing the modern tools using scientific innovations in, biology,
genomics and proteomics to mitigate AMR pathogens
• Search for new antibiotics
• Development and strengthening of the use of conventional alternatives
to antibiotics
– Chemical antimicrobials (also called biocides and antimicrobial pesticides) are often
used as antiseptics, disinfectants, and sterilizers, sanitisers
• Organic
• Inorganic
– Herbal antimicrobials
– Antiserum- Serum therapy & Monoclonal antibodies
– Vaccines: Not to discuss
– Repurposing the drugs
– Homeopathy
– Acupuncture and Acupressure
– Bhabhut/ Ashes/ Fumes/ Mantras

8. Scope of alternate antimicrobials
Globally about 35 billion doses of antibiotics (3500-5000 tons) are
used for therapy and disease prevention in human medicine and
about 50000 tons for treatment and growth promotion in the
livestock and agriculture sectors. Estimates were >100,000
tonnes of antibiotics used in livestock (OIE, 2019).
However, the Centre for Disease Dynamics, Economics & Policy
(CDEEP, 2021) found that in 2013, the global consumption of all
antimicrobials in food animals was 131,109 tonnes and is
projected to reach 200,235 tonnes by 2030.
CDDEP report, global antibiotic consumption increased by 65%
between 2000 and 2015, and the rate of antibiotic consumption
increased by 39%, 32 from 11.3 to 15.7 defined daily doses
(DDDs) per 1,000 people.
From 2000 to 2015: Globally, total antibiotic consumption in humans
soared 65%. In India 103% increase, China 79%, and in Pakistan
65% increase (Center for Disease Dynamics, Economics & Policy, 2018).

9. Herbal antimicrobials
Bhardwaj et al., 2016. Pharmaceutica Analytica Acta 7(11):1-4. DOI: 10.4172/2153-2435.1000523
• Alcaloids: Piperine (Pier longum, Piper nigrum), Berberine
(Berberis vulgaris), Reserpine (Rauwolfia serpentina).
• Organosulphur compounds: Allicin (Allium sativum)
• Terpenes: Carvone, Eugenol, Linelool, Thymol, Carvacrol
(cymophenol, C₆H₃C₃H₇), is a mono-terpenoid phenol.
• Cinnamaldehyde, C₆H₅CH=CHCHO is a phenyl-propanoid,
naturally synthesized by the shikimate pathway.

10. 7.0
16.5
12.6
13.3
17.1
59.8
52.8
89.4
38.9
82.1
81.0
64.7
43.3
93.9
74.3
61.2
76.9
83.5
77.1
75.2
58.6
72.1
73.3
95.3
0.0 20.0 40.0 60.0 80.0 100.0 120.0
Carvacrol
Ajowan oil
Thyme oil
Cinnamledehyde
Cinnamon oil
Lemongrass oil
Citral
Citronella
Holy basil oil
Agarwood Oil
Ageratum conizoides methanolic extract
Ashoka (Polyalthia longifolia) seed ether extract
Betel leaf oil
Caraway oil
Eupatorium odoratus leaves methanolic extract
Gooseberry (Polyanthus emblica)leaves…
Guggul oil
Kalonji methanolic extract
Marjoram oil
Patchouli oil
Rosewood oil
Sandalwood oil
Zanthoxylum rhetsa seed methanolic extract
Zanthoxylum rhetsa seed oil
Percent resistant strains (tested on ~8000 bacterial strains)

11. 57.4
25.4
38.0
54.4
29.4
62.4
8.7
31.5
39.7
29.7
21.3
33.7
41.4
38.9
21.7
16.4
45.6
18.6
29.6
61.6
41.0
67.4
39.3
43.6
11.7
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0
ESBL positive
Amikacin
Amoxi+clavulanic acid
Amoxicillin
Amoxicillin+sulbactam
Ampicillin
Ampicillin+sulbactam
Cefotaxime
Ceftazidime
Ceftazidime+Clavulanic acid
Chloramphenicol
Ciprofloxacin
Cotrimoxazole
Doxicycline
Gentamicin
Imipenem
Kanamycin
Meropenem
Minocycline
Nalidixic acid
Nitrofurantoin
Penicillin
Streptomycin
Tetracycline
Tigecycline
Percent resistant strains (tested on ~8000 bacterial strains)

12. 0.00
20.00
40.00
60.00
80.00
100.00
120.00
Tetracycline Susceptible Tetracycline Resistant
Chloramphenicol Susceptible Chloramphenicol Resistant
Tetracycline and chloramphenicol resistant bacteria are more
resistant to herbal antimicrobials than the susceptible strains.
Susceptibility of clinical and environmental bacterial
strains to herbal antimicrobials

13. Susceptibility of clinical and environmental bacterial
strains to herbal antimicrobials
0.00
20.00
40.00
60.00
80.00
100.00
120.00
Ciprofloxacin Susceptible Ciprofloxacin Resistant
Gentamicin Susceptible Gentamicin Resistant
Ciprofloxacin-resistant
bacteria were more often
susceptible to Ajowan oil
than Cipro-susceptible
strains.
Gentamicin-resistant
strains were more
susceptible to Carvacrol
than gentamicin
susceptible strains.
For other herbals Genta
and Cipro-Resisatnt
strains were also more
resistant than susceptible
strains.

14. Susceptibility of clinical and environmental bacterial
strains to herbal antimicrobials
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
Non-ESBL Producers ESBL Producers
ESBL Producers Carbapenem Resistant Non ESBL Producers Carbapenem Susceptible
ESBL producing bacteria
were more susceptible than
non-ESBL producers to
Ajowan oil, HBO,
Cinnamaldehyde, Thyme
oil, & Cinnamon oil.
Strains not producing ESBL
and susceptible to
carbapenems were more
resistant to Ajowan oil than
strains resistant to
carbapenems and

15. Susceptibility of clinical and environmental bacterial
strains to herbal antimicrobials
0.00
20.00
40.00
60.00
80.00
100.00
120.00 Nitrofurantoin Susceptible Nitrofurantoin Resistant
Carbapenem Susceptible Carbapenem Resistant Nitrofurantoin or
carbapenem
susceptible strains
were more often
susceptible to herbal
antimicrobials than
nitrofurnatoin or
carbapenem resistant
strains

16. Therapeutic use of herbs as antimicrobials
Antimicrobial Herbals Dose in grams or mL for Therapeutic use (Oils are given mixed in
blend oil)
Cattle Horse Dogs
Clove (Lavang) powder 8-15 4-8 0.3-0.6 Gastrointestinal infections, chronic
diarrhoea
Clove (Eugenia caryophyllus) oil 1-2.6 1-1.5 0.03-0.2
Caraway (Shahjeera) powder 30-60 30-60 0.6-2 Gastrointestinal infections, chronic
diarrhoea, tympany
Caraway (Carum carvi) oil 1-2.6 1-1.5 0.03-0.2
Coriander (Coriandrum sativum) 15 15 Urethritis
Soya (Anethum graveolens) seed 30-60 30-60 0.6-2 Gastrointestinal infections, chronic
diarrhoea, tympany
Soya (Anethum or Dill) oil 1-2.6 1-1.5 0.03-0.2
Cinnamon (Dalchini) powder 8-15 8-15 0.6-1 Gastrointestinal infections, chronic
diarrhoea, dysentery
Cinnamon (Cinnamomum zeylanicum) oil 1-2.6 1-1.5 0.03-0.2
Nutmeg (Jaiphal) powder) 8-15 8-15 0.3-0.6 Gastrointestinal infections, chronic
diarrhoea, dysentery
Nutmeg (Myristica fragrans) oil 0.06-0.2
Turpentine oil 15 15 Gastrointestinal infections
Eucalyptus globulus oil 4-15 4-15 0.03-0.2 Wounds, surgical wound, respiratory tract
infections
Cajuput (Melaleuca leucadendron) oil 0.06-0.2 Pneumonia and bronchitis & arthritis
Garlic (Allium sativum) paste 8-15 8-15 0.3-0.6 Gastrointestinal infections
Garlic oil and Garlic juice 4 times diluted for external Wound, ringworm, ear infection, ulcers,
maggots
Onion (Allium cepa) juice Fresh juice Otorrhoea, bronchitis
Cubeb (Kababchini) powder 15-30 15-30 1-4 Urinary tract infection, genital tract
infection, respiratory tract infection,
chronic cough
Cubeb (Piper cubeba) oil 4-15 4-15 0.3-1
Copaiba (Oleoresin from trunk of Copaifera tree) 8-24 8-24 0.3-2 Urinary tract infection
Sandalwood (Santalum albus) oil 0.3-1.3 Mild Urinary tract infection
Buchu (Barosma betulina) extract or infusion
(Buchu leaves 20 g in 100 mL of 60% Alcohol)
30-60 30-60 2-4 Mild Urinary tract infection
Juniper (Juniperus communis) oil 4-8 4-8 0.3-0.6 Nephritis, cystitis, urethritis

17. Limitation of Herbal antimicrobial therapy
• Quality, and Quality control: No or only
preliminary
• Availability in required quality and quantity
• Therapeutic doses ill-defined.
• Lack of Evidence-based literature.
• Systemic use problems
• Safety and toxicity problems
• No standard Pharmacopeia
• Herbal drug resistance and cross-resistance to
antibiotics.
• Misconceptions

18. Strength and weakness of Herbal
Antimicrobials
• Some are really very effective antimicrobials even more than the
best antibiotics.
• Corrosive/ irritant/ non-soluble in an aqueous system.
• Herbal antimicrobials lose antimicrobial potential when added
with common excipients like blending oils/ ointment bases. The
two most potent herbal antimicrobials, Thyme and Ajwain oils (2%),
completely lost their antibacterial activity in vegetable oils and
liquid paraffin. However, Cinnamon oil, another potent herbal
antimicrobial, lost its antimicrobial activity significantly in all the
excipients compared to Dimethyl-Sufoxide as a diluent. Among
vegetable oils, olive oil followed by palm oil, mustard oil, sesame oil
and coconut oil retained the antimicrobial activity of cinnamon oil
to a variable extent.
https://www.researchgate.net/publication/351761448_Excipient_effec
t_on_antimicrobial_activity_of_cinnamon_Cinnamomum_zelylanic
um_album_oil_thyme_Thymus_vulgaris_oil_and_ajowan_Trachysp
ermum_ammi_oil.

19. Future Research
• Better delivery systems (non-toxic, targeted):
Nano-formulations
• Methods for Quality Assurance
• Clinical studies for dose and regimen
standardization

20. Publications on Herbal antimicrobials from our Laboratory
• https://www.researchgate.net/publication/312218154_Potential_of_Herbal_Drug_and_Antibiotic_Combination_Therapy_A_New_Approach_to_Treat_Mul
tidrug_Resistant_Bacteria
• https://www.researchgate.net/publication/364358447_Evaluation_of_Fifatrol_Septilin_Giloy_Guduchi_Tinospora_cordifolia_and_Oils_of_Guggul_Balsamo
dendron_mukul_and_Holy_Basil_Tulsi_Ocimum_sanctum_for_their_Antimicrobial_Potential
• https://www.researchgate.net/publication/362582264_Comparative_Antimicrobial_Efficacy_of_Methanolic_and_Diethyl_Ether_Extracts_of_Rose_Rosa_In
dica_Hip_Seeds_Against_Clinically_Important_Microbes_in_Journal_of_Herbal_Medicine_and_Medicinal_Plants
• https://www.researchgate.net/publication/361815000_In_vivo_therapeutic_efficacy_of_Curcuma_longa_extract_loaded_ethosomes_on_wound_healing
• https://www.researchgate.net/publication/359218614_Conventional_and_non-conventional_Antibiotic_alternatives
• https://www.researchgate.net/publication/359281155_padapiya_jivanu_rodhi_ya_padapiya_padapiya_pratijaivika_arthata_harbala_entibayotiksa
• https://www.researchgate.net/publication/356633917_Antibiotic_alternatives_in_Veterinary_Therapeutics
• https://www.researchgate.net/publication/355166327_Alternative_Approaches_to_Mitigate_Antimicrobial_Drug_Resistance
• https://www.researchgate.net/publication/351761448_Excipient_effect_on_antimicrobial_activity_of_cinnamon_Cinnamomum_zelylanicum_album_oil_t
hyme_Thymus_vulgaris_oil_and_ajowan_Trachyspermum_ammi_oil
• https://www.researchgate.net/publication/346413819_Potential_of_Herbal_Antibacterials_as_an_Alternative_to_Antibiotics_for_Multiple_Drug-
Resistant_Bacteria_An_Analysis
• https://www.researchgate.net/publication/341150440_Herbal_antimycotics_and_their_prospects
• https://www.researchgate.net/publication/330676498_Antimicrobial_Activity_of_Agarwood_Oil_Against_Multiple-Drug-
Resistant_MDR_Microbes_of_Clinical_Food_and_Environmental_Origin
• https://www.researchgate.net/publication/337146176_MexAB-
OprM_efflux_pump_of_Pseudomonas_aeruginosa_offers_tolerance_to_carvacrol_A_herbal_antimicrobial_agent
• https://www.researchgate.net/publication/338036703_Herbal_antimicrobials_and_their_Future-
_harbala_roganurodhi_aura_unaka_bhavisya_in_Shalihotra_Darshan_2019_ICAR-IVRI
• https://www.researchgate.net/publication/334925315_Comparative_antimicrobial_activity_of_Pogostemon_cablin_patchouli_essential_oil_PEO_and_con
ventional_antimicrobials_against_clinically_important_microbes
• https://www.researchgate.net/publication/335003680_Epidemiology_of_carvacrol_resistant_Pseudomonas_aeruginosa_isolates_from_raw_milk
• https://www.researchgate.net/publication/334225077_Evaluation_of_carvacrol_as_an_antibacterial_agent_against_Escherichia_coli_isolated_from_differ
ent_animal_species
• https://www.researchgate.net/publication/328633399_Comparative_Antimicrobial_Activity_of_Herbal_and_Conventional_Antimicrobials_on_Enteric_Bac
teria_Isolated_from_Intestinal_Contents_of_Dead_Domesticated_and_Non-domesticated_Birds
• https://www.researchgate.net/publication/325083229_Studies_on_Synergy_Between_Trans-
Cinnamaldehyde_and_Selected_Antibiotics_Using_Escherichia_coli_Model
• https://www.researchgate.net/publication/330709265_In_vitro_Evaluation_of_Some_Herbal_Compounds_on_Fungi_Isolated_from_Clinical_Cases_in_Ani
mals_and_their_Associated_Environment
• https://www.researchgate.net/publication/318877064_Antimicrobial_Activity_of_Kalonji_Oil_and_its_Comparison_with_Methanolic_and_Aqueous_Extra
cts_of_Nigella_sativa_Kalonji_Seeds
• https://www.researchgate.net/publication/320166069_Molecular_Studies_on_Resistance_against_Carvacrol_in_Escherichia_coli_Pseudomonas_aeruginos
a
• https://www.researchgate.net/publication/321420361_Antimicrobial_resistance_profile_of_enteropathogens_isolated_from_diarrhea_patients_Herbal_an
timicrobials_a_ray_of_hope
• https://www.researchgate.net/publication/312218154_Potential_of_Herbal_Drug_and_Antibiotic_Combination_Therapy_A_New_Approach_to_Treat_Mul
tidrug_Resistant_Bacteria
• https://www.researchgate.net/publication/312213824_Comparative_Antimicrobial_Activity_of_Tea_Tree_Oil_Melaleuca_Oil_and_Common_Topical_Anti
microbials_against_Bacteria_Associated_With_Wound_and_Topical_Infections
• https://www.researchgate.net/publication/305722345_Effect_of_Herbal_Antimicrobials_on_Bacterial_Strains_of_Foods_of_Vegetable_and_Animal_Origin
_Open_Access

21. • https://www.researchgate.net/publication/298338460_Antimicrobial_Activity_in_Aqueous_and_Methanolic_Leaf_Extract_of_Eupa
torium_odoratum_against_Bacteria_of_Clinical_and_Nonclinical_Origin
• https://www.researchgate.net/publication/301700346_Antimicrobial_Activity_of_Methanolic_Extract_and_Ether_Extract_of_Ager
atum_conyzoides
• https://www.researchgate.net/publication/299599050_Antimicrobial_and_herbal_drug_resistance_pattern_of_important_pathoge
ns_of_animal_health_importance_at_Bareilly
• https://www.researchgate.net/publication/298790017_Antimicrobial_activity_of_ethanolic_and_aqueous_extracts_of_common_e
dible_gums_against_pathogenic_bacteria_of_animal_and_human_health_significance
• https://www.researchgate.net/publication/286035483_Antimicrobial_Activity_of_Citronella_Essential_Oil_on_Antimicrobial_Drug
_Resistant_Bacteria_from_Veterinary_Clinical_Cases
• https://www.researchgate.net/publication/283352721_Antimicrobial_Activity_of_Natural_Edible_Gums
• https://www.researchgate.net/publication/283638352_Antimicrobial_activity_of_Commiphora_wightii_gum_Guggul_gum_extract
_against_gram_positive_and_gram_negative_bacteria
• https://www.researchgate.net/publication/281022423_Antimicrobial_Activity_of_Rose_Geranium_Pelargonium_roseum_Essential
_Oil_on_Bacteria_of_Veterinary_Clinical_Origin
• https://www.researchgate.net/publication/274255982_Antibacterial_activity_of_Caraway_essential_oil_against_bacteria_isolated
_from_veterinary_clinical_cases
• https://www.researchgate.net/publication/307780999_Antimicrobial_Activity_of_Citronella_Essential_Oil_on_Antimicrobial_Drug
_Resistant_Bacteria_from_Veterinary_Clinical_Cases
• https://www.researchgate.net/publication/283859908_Emergence_of_Herbal_Antimicrobial_Drug_Resistance_in_Clinical_Bacteria
l_Isolates
• https://www.researchgate.net/publication/274570042_Multiple-herbal-antimicrobial-
resistance_MHAR_in_microbes_of_animals_birds_fish_food_lizard_and_water_origin
• https://www.researchgate.net/publication/264047281_Antibacterial_Activity_of_Glycerol_Lactose_Maltose_Mannitol_Raffinose_a
nd_Xylose
• https://www.researchgate.net/publication/258831812_Evaluation_of_Antibacterial_Activity_of_Sage_Salvia_officinalis_Oil_on_Ve
terinary_Clinical_Isolates_of_Bacteria
• https://www.researchgate.net/publication/258504727_Antimicrobial_and_Herbal_Drug_Resistance_in_Enteric_Bacteria_Isolated_f
rom_Faecal_Droppings_of_Common_House_LizardGecko_Hemidactylus_frenatus
• https://www.researchgate.net/publication/287534302_Comparative_evaluation_of_antimicrobial_effect_of_Artemisia_vulgaris_es
sential_oils_extracted_from_fresh_and_dried_herb
• https://www.researchgate.net/publication/260198629_Antimicrobial_activity_on_common_pathogens_in_essential_oil_of_aerial_
parts_of_Selinum_wallichianum
• https://www.researchgate.net/publication/260198619_Comparative_evaluation_of_antimicrobial_effect_of_Artemisia_vulgaris_es
sential_oils_extracted_from_fresh_and_dried_herb
• https://www.researchgate.net/publication/260173692_Antimicrobial_activity_of_lemongrass_Cymbopogon_citratus_oil_against_
microbes_of_environmental_clinical_and_food_origin
• https://www.researchgate.net/publication/260198514_Antimicrobial_Effect_of_Artemisia_Vulgaris_Essential_Oil